Herbal medicines for the treatment of cardiovascular diseases: Benefits and risks - A narrative review.

Herbal medicines (HMs) have been traditionally used for the prophylaxis/treatment of cardiovascular diseases (CVDs). Their use is steadily increasing and many patients with CVDs often combine HMs with prescribed cardiovascular medications. Interestingly, up to 70% of patients do not notify cardiologists/physicians the use of HMs and up to 90% of cardiologists/physicians may not routinely inquire them about the use of HMs. There is limited scientific evidence from well-designed clinical trials supporting the efficacy and safety of HMs and because they do not reduce morbidity and mortality are not recommended in clinical guidelines for the prophylaxis/treatment of CVDs. There is also a great deal of confusion about the identification, active constituents and mechanisms of action of HMs; the lack of standardization and quality control (contaminations, adulterations) represent other sources of concern. Furthermore, the widespread perception that unlike prescription drugs HMs are safe is misleading and some HMs can cause clinically relevant adverse events and interactions, particularly when used with narrow therapeutic index prescribed cardiovascular drugs (antiarrhythmics, antithrombotics, digoxin). Cardiologists/physicians can no longer ignore the problem. They must improve their knowledge about the HMs their patients consume to provide the best advice and prevent adverse reactions and drug interactions. This narrative review addresses the putative mechanisms of action, suggested clinical uses and safety of most commonly used HMs, the pivotal role of cardiologists/physicians to protect consumers and the main challenges and gaps in evidence related to the use of HMs in the prophylaxis and treatment of CVDs.

Flavonoids: Antiplatelet Effect as Inhibitors of COX-1.

Flavonoids are compounds with a benzopyranic structure that exhibits multiple pharmacological activities. They are known for their venotonic activity, but their mechanism of action remains unclear. It is thought that, as this mechanism is mediated by prostaglandins, these compounds may interfere with the arachidonic acid (AA) cascade. These assays are designed to measure the antiplatelet aggregation capacity of quercetin, rutin, diosmetin, diosmin, and hidrosmin, as well as to evaluate a potential structure-activity ratio. In this paper, several studies on platelet aggregation at different concentrations (from 0.33 mM to 1.5 mM) of different flavone compounds are conducted, measuring platelet aggregation by impedance aggregometry, and the cyclooxygenase (COX) activity by metabolites generated, including the activity of the pure recombinant enzyme in the presence of these polyphenols. The results obtained showed that quercetin and diosmetin aglycones have a greater antiplatelet effect and inhibit the COX enzyme activity to a greater extent than their heterosides; however, the fact that greater inhibition of the pure recombinant enzyme was achieved by heterosides suggests that these compounds may have difficulty in crossing biological membranes. In any case, in view of the results obtained, it can be concluded that flavonoids could be useful as coadjuvants in the treatment of cardiovascular pathologies.

A New Approach to the Management of COVID-19. Antagonists of IL-6: Siltuximab.

Since the beginning of the pandemic, numerous national and international clinical trials have been conducted with a large number of drugs. Many of them are intended for the treatment of other pathologies; however, despite the great effort made, no specific drug is available for the treatment of the symptoms of respiratory disease caused by SARS-CoV-2 infection. The aim of this article is to provide data to justify the use of drugs to tackle the effects produced by IL-6 as the main inflammatory mediator in patients with COVID-19 with severe respiratory complications, considering all clinical evidence linking the poor prognosis of these patients with increased IL-6 levels in the context of cytokine release syndrome. Furthermore, data are provided to justify the proposal of a rational dosing of siltuximab, a monoclonal antibody specifically targeting IL-6, based on RCP levels, considering the limited results published so far on the use of this drug in COVID-19. A literature search was conducted on the clinical trials of siltuximab published to date as well as on the different IL-6 signalling pathways and the effects of its overexpression. Knowledge of the mechanisms of action on these pathways may provide important information for the design of drugs useful in the treatment of these patients. This article describes the characteristics, properties, mechanism of action, therapeutic uses and clinical studies conducted with siltuximab so far. The results confirm that administration of siltuximab downregulates IL-6 levels, thereby reducing the inflammatory process in COVID-19 patients with severe respiratory disease, suggesting that it can be successfully used to prevent cytokine release syndrome and death from this cause.

Binding and antiplatelet activity of quercetin, rutin, diosmetin, and diosmin flavonoids.

Platelets exert an essential role in vascular inflammation and thrombosis. Flavonoids are natural compounds employed for the clinical management of vascular disorders preventing capillary permeability, working as phlebotonics and improving the blood rheology, although their mechanism of action remains partially unknown. The effects of quercetin, rutin, diosmetin and diosmin were investigated in platelet activation utilizing blood from healthy and non-treated volunteers. The arrangement of the different activation states of platelets and GPIIb/IIIa receptor occupation was computed by flow cytometry working with calcium ionophore as pro-aggregant to provoke platelet activation and aggregation. The flavonoids studied demonstrated relevant antiplatelet activity through the blocked of GPIIb/IIIa receptors, the suppression of the platelet activation, as well as the pro-aggregate effect of calcium ionophore. Therefore, whichever of the active ingredients examined could be beneficious in the prevention of cardiovascular disease and this article also contributes to elucidate a new mechanism of action for these drugs.

Antiplatelet Activity of Coumarins: In Vitro Assays on COX-1.

Atherosclerotic cardiovascular disease is the leading cause of death in developed countries. Therefore, there is an increasing interest in developing new potent and safe antiplatelet agents. Coumarins are a family of polyphenolic compounds with several pharmacological activities, including platelet aggregation inhibition. However, their antiplatelet mechanism of action needs to be further elucidated. The aim of this study is to provide insight into the biochemical mechanisms involved in this activity, as well as to establish a structure-activity relationship for these compounds. With this purpose, the antiplatelet aggregation activities of coumarin, esculetin and esculin were determined in vitro in human whole blood and platelet-rich plasma, to set the potential interference with the arachidonic acid cascade. Here, the platelet COX activity was evaluated from 0.75 mM to 6.5 mM concentration by measuring the levels of metabolites derived from its activity (MDA and TXB2), together with colorimetric assays performed with the pure recombinant enzyme. Our results evidenced that the coumarin aglycones present the greatest antiplatelet activity at 5 mM and 6.5 mM on aggregometry experiments and inhibiting MDA levels.

Potential Therapeutic Anti-Inflammatory and Immunomodulatory Effects of Dihydroflavones, Flavones, and Flavonols.

Systemic inflammation, circulating immune cell activation, and endothelial cell damage play a critical role in vascular pathogenesis. Flavonoids have shown anti-inflammatory effects. In this study, we investigated the effects of different flavonoids on the production of pro-inflammatory interleukin (IL) 1ß, 6, and 8, and tumor necrosis factor α (TNF-α), in peripheral blood cells. Methods: We studied the whole blood from 36 healthy donors. Lipopolysaccharide (LPS)-stimulated (0.5 µg/mL) whole-blood aliquots were incubated in the presence or absence of different concentrations of quercetin, rutin, naringenin, naringin, diosmetin, and diosmin for 6 h. Cultures were centrifuged and the supernatant was collected in order to measure IL-1ß, TNF-α, IL-6, and IL-8 production using specific immunoassay techniques. This production was significantly inhibited by quercetin, naringenin, naringin, and diosmetin, but in no case by rutin or diosmin. Flavonoids exert different effects, maybe due to the differences between aglycons and glucosides present in their chemical structures. However, these studies suggest that quercetin, naringenin, naringin, and diosmetin could have a potential therapeutic effect in the inflammatory process of cardiovascular disease.

Antiplatelet activity of flavonoid and coumarin drugs.

Polyphenols are used as phlebotonic drugs, but their mechanism of action remains unknown. Since platelet activity and platelet-endothelial cell interactions are involved in the pathogenesis of cardiovascular disease, this work examines whether different flavonoid and coumarin drugs are able to inhibit platelet aggregation. This specific case of coumarins, the antiplatelet effect is not linked with a possible interaction over blood coagulation since this effect only dicoumarols have it. The antiplatelet capacity of polyphenols was assayed using peripheral blood platelets from healthy controls. The distribution of the different platelets subsets was quantified by flow cytometry, using the calcium ionophore as a pro-aggregant. The number of GPIIb/IIIa receptors occupied by the drugs was assayed by flow cytometry using two CD61 surface fluorescein antibodies. All the polyphenols tested inhibited platelet aggregation. A percentage antiplatelet activity of 88.91±7.98% was recorded for naringin, 48.43±8.84% for naringenin, 53.83±7.87% for esculetin, 54.65±6.91% for fraxetin, and 25.75±4.12% for coumarin. Naringin showed significantly greater percentage occupation of GPIIb/IIIa receptors than did naringenin (14.82±0.81% vs. 3.90±0.55%), and esculetin returned significantly higher values than fraxetin and coumarin (12.47±0.97 vs. 7.53±0.49 and 7.90±0.69 respectively). All drugs show important antiplatelet activity. Naringin was the best antiplatelet compound, showing the greatest antiplatelet activity and the highest percentage binding of GPIIb/IIIa receptors. However, any of the compounds used could be used in the prevention of cardiovascular disease.

Antiviral activity of seven iridoids, three saikosaponins and one phenylpropanoid glycoside extracted from Bupleurum rigidum and Scrophularia scorodonia.

As part of our screening of antiviral agents from medicinal plants, 11 compounds from plant origin (Bupleurum rigidum and Scrophularia scorodonia), three saikosaponins, seven iridoids and one phenylpropanoid glycoside were tested in vitro against herpes simplex type I (HSV-1), vesicular stomatitis virus (VSV) and poliovirus type 1. Five of these compounds showed antiviral activity against VSV. The percentages of cellular viability at the non-toxic limit concentrations of the active compounds were: verbascoside 53.6 % at 500 microg/ml, 8-acetylharpagide 32.1 % at 500 microg/ml, harpagoside 43.3 % at 450 microg/ml, scorodioside 47.8 % at 500 microg/ml and buddlejasaponin IV 56.9 % at 25 microg/ml. Although none of the saikosaponins were active against HSV-1, the iridoid scorodioside showed moderate in vitro anti-HSV-1 activity (30.6 % at 500 microg/ml). However, none of the compounds tested in this survey had any effect against poliovirus.

Sesquiterpenes from Jasonia glutinosa: in vitro anti-inflammatory activity.

Four sesquiterpenes isolated from Jasonia glutinosa D.C. (Asteraceae), namely lucinone, glutinone, 5-epi-kutdtriol and kutdtriol, have been evaluated for their in vitro anti-inflammatory activity in cellular systems generating cyclooxygenase (COX) and 5-lipoxygenase (5-LOX) metabolites. None of the compounds assayed had a significant effect on leukotriene C4 (LTC4)-release from calcium ionophore-stimulated mouse peritoneal cells. However, the release of prostaglandin E2 (PGE2) by mouse peritoneal cells stimulated with calcium ionophore was inhibited by these compounds, although with less potency than the reference drug indomethacin (IC50=0.24 microM). The IC50 values of the active compounds were: lucinone 42.69 microM, glutinone 3.61 microM, 5-epi-kutdtriol 1.28 microM and kutdtriol 39 microM. Of the tested compounds, only glutinone (IC50=24 microM) showed a significant effect on thromboxane B2 (TXB2)-release induced by calcium ionophore in human platelets, although with less potency than the reference drug ibuprofen (IC50=1.27 microM).